This invention relates to a skeleton discharge mechanism for use with various types of blanking presses such as cupmaker blank and draw presses and the like. More particularly, the skeleton discharge mechanism of the present invention is uniquely constructed capable of discharging scrap skeleton sheets on a completely positive basis at a timed rate compatible with modern production presses. According to the present invention, the mechanism operates to securely engage a leading edge portion of each scrap skeleton sheet as the press operations thereon are completed, and during maintainment of such secure engagement, positively moves the scrap skeleton sheet through the scrap discharge mechanism and therefrom to final discharge. In a preferred optimum form, the mechanism is preferably fully selectively adjustable for adapting the same to a wide range of different scrap skeleton sheet sizes so that a single model of such mechanism through these selective adjustments is usable with various different dies of a given press or various different presses.
Many forms of skeleton discharge mechanisms have heretofore been provided incorporated directly in or as separate auxiliary equipment with various types of solely blanking or combined blank and draw presses. One very common use of blank and draw presses is in the manufacture of two-piece metallic can bodies, that is, a single-piece can body with integral side and bottom walls sealed by a can end after filling with its intended contents. In any event, all such presses produce scrap skeleton stock either in sheet or strip form requiring subsequent discharge and ultimate disposal.
Although coil fed, continuous strip blank and presses are used in the can making industry and the principals of the present invention would have certain application therewith, a large number of sheet fed blank and draw presses are likewise used. For instance, due to certain technicalities of adding and maintaining coated surfaces of the materials, it is necessary that the material supplied to the blank and draw presses will be separate sheet form. Thus, although again it is clear to those skilled in the art that most of the same problems exist with coil fed blank and draw presses, the present discussion is confined to sheet fed blank and draw presses.
With sheet fed blank and draw presses, the sheets are fed at appropriate time intervals, one at a time, longitudinally into proper start position in the blank and draw press. On the first stroke of the press, transverse rows of cup blanks, usually two or more rows appropriately spaced and internested for maximum material usage, are removed from the sheet at the leading edge portion thereof. At the completion of the first press stroke and during iniation of the second press stroke, the sheet is indexed longitudinally by the press exposing longitudinally adjacent sheet material for removal of a second multiplicity of cup blanks, such press stroking and sheet indexing continuing, usually five or six times, until the trailing end portion of the sheet is reached and the last rows of cup blanks are removed. The result is that as the last press stroke is completed for a given sheet, the leading edge portion of the sheet projects longitudinally from the press and the entire sheet is filled with a maximum number of closely spaced cup blank or part holes thereby constituting a scrap skeleton sheet.
It is the problems involved from this stage of operation on with which the principals of the present invention are involved, that is, just how to remove these scrap skeleton sheets from the press on a consecutive basis. One of the problems encountered is occasioned by the fact that modern day metallic cans, whether the shallow food containers or the deeper beverage containers, are formed from extremely thin metal in the order of a few thousandths of an inch so that the scrap skeleton sheets in widths up to about forty-two inches and lengths up to about forty-four inches comprised of a maximum of holes interconnected by thin metal sections are extremely fragile. It is virtually impossible to push these fragile scrap skeleton sheets from the press since they are not of sufficient overall rigidity to withstand such forces from these locations, although such is occasionally done with the aid of gravity where it is possible to tilt the press to a relatively sharp angle but which, in operations of the type herein involved, presents many additional problems.
A second important factor involves the small time interval permitted for removal of these fragile scrap skeleton sheets from the press in modern press operations and particularly in modern can cupmaker blank and draw press operations. For instance, a modern can cupmaker blank and draw press operates at speeds in the order of one hundred to one hundred ten strokes or cycles per minute and with five sheet indexes to complete each sheet and produce a scrap skeleton sheet. This means that the scrap skeleton sheets must be discharged or removed from the press at the rate of twenty to twenty-two sheets per minute. Assuming the minimum rate of operation, the time interval allowed for the complete removal of a scrap skeleton sheet from the press is three seconds and it is obvious that any attempt to frictionally engage the scrap skeleton sheet, such as with friction rolls, and accelerate the same from its stationary position to movably discharge it from the press would be completely undependable, if not impossible resulting in serious complications to press dies and other equipment upon any failure.